


Metamorphosis

by AmbroseRivers



Series: Undertale Collection [2]
Category: Bishoujo Senshi Sailor Moon | Pretty Guardian Sailor Moon, Undertale (Video Game)
Genre: Alternate Universe - Underswap, Crossover, F/F, F/M, M/M, Multi
Language: English
Status: In-Progress
Published: 2016-04-12
Updated: 2016-04-12
Packaged: 2018-06-01 19:41:39
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 2,394
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6533824
Author URL: https://archiveofourown.org/users/AmbroseRivers/pseuds/AmbroseRivers
Summary: <blockquote class="userstuff">
              <p>She is desperate to get home and where the hell was she anyway? Living monsters, a tall lazy skeleton and his energetic brother, losing control of her Senshi powers and knowing she's supposed to be there and not here? She is desperate to find her way out.</p><p>...Or maybe it's not as bad as she thought.</p><p>*A series of connected drabbles.*</p>
            </blockquote>





	1. -Yearning for Home-

**Author's Note:**

> This is a crossover for Sailor Moon/Underswap. It is going to revolve around an OC so if that is not your thing, please find another story you may enjoy! <3 I am very rusty in my writing so if there are errors, feel free to let me know. 
> 
> This is crossposted from my tumblr: loveinthebones.tumblr.com/ 
> 
> These drabbles may update sporadically.

Her hair was singed and she was _tired._ Her pink boots scraped the stone as she spun to avoid the flames crackling around her.

_God damn it! I don’t want to FIGHT. That frog told me I didn’t HAVE to so let me PASS PLEASE!_

Her fingers itched to call her tiara into play but… she couldn’t. She wouldn’t. There had to be a better way- she had been told there was a better way.

Sailor Cat raised her head proudly, feeling her magic spin around her restlessly and she let of a breath as wisps of red, cyan, black, and aqua mixed with pink. It was a relief to know that her sister’s gifted sigils hadn’t left her and Cat focused her mind on the red.

“Fight fire with fire!” She heard Star Mars say with gritted teeth and let the warmth travel down her hands.

_No. Defend. No fighting._

Cat jumped with a snarl. “Let me pass!”

Asgore’s eyes flashed regretfully for a moment, trident still in hand but he gripped it tighter. His white ears trembled and his fangs snapped together with an audible click as he raised the trident and more white flames formed.

Cat ground her teeth and willed the violent red wisps to bend to her will and gasped at the unexpected pain across her palm. What the hell? Her eyes darted to her hand quickly, taking note of the growing redness and bubbling skin. It seems that the sigils wouldn’t be easily swayed here- she pushed away the accompanying _Where is this?_ From her mind- but it wouldn’t matter.

She just needed a moment.

Asgore’s fire rushed to her, air hissing and the stench of burnt ozone filling her nose as she hopped between falling fire and the vicious glint of the trident.

“I’m trying to save you! She…Tori…will kill you! Do you want that?”

As a Senshi, battling things that wanted to kill her wasn’t anything new but the unstable state of her transformation was as the blessed crests that refused to function the way she wanted. Her brooch flickered as if reading her thought and she cried out as her skin sizzled with heat. Her eyes watered and she pressed against the raw wound on her thigh, tears spilling out.

“I…please, Asgore. I want to go home.” _I **need** to be home._

The trident stopped swinging and Asgore’s expression was pained as she stood once more. Her vision spun and her knees shook. She felt weak and Asgore lowered his weapon.

“Mars Star Flame!” She cried and the magic ripped free from her palm, spiraling around her in a controlled tempest and Cat took a slow step.

“I do not want to fight. I will be okay… I promise. Please…” The heat from Reiko’s symbol wasn’t painful but she was sweating, multi-colored skirt sticking to her legs. “Let…let me pass.”

“I…” Asgore lowered his head and he laughed a broken, hollow sound. “I just wanted to save them. The children…the humans…that passed through. I couldn’t save them but…” His breath hitched and wet stripes matted his fur as he looked at Cat. He took a shaky breath. “I couldn’t save you. I wanted to.”

The embers that glowed along the stone and soot that streaked the ground disappeared with a wave of his palm and Cat dropped to a knee, weak with relief.

_Release._

Cat could see the mark of Sailor Star Mars burn brightly in her vision before the flame-inspired magic died in a violent burst. She watched the red glittering wisps rain before raising her gaze to Asgore and smiled.

“You saved me. By letting me pass…I’ll…” Cat paused and bit her lip. What would a lie hurt? She had no idea where she was and really… a little hope couldn’t hurt.

_That much._ Her mind whispered as the world swayed around her. She needed to rest and find some more items to help her heal.

“I’ll be back later. Then we’ll catch a cup a tea, eh, Dad?” Cat chuckled as she rose to her full height and stumbled to embrace Asgore. The Senshi winced as he hugged her tightly back, breath ragged. He said nothing at the mention of their tea but she knew that he knew it was a lie…

He would lock the door after her.

“Just…take care of yourself out there.” He murmured before releasing her and draping a purple cloak around her. She squeaked as the heavy material pulled her already unsteady frame- fighting to muffle a quiet groan when it brushed her charred skin but she tilted her head.

Asgore refused to look at her.

“You might need that.” His eyes finally settled on her fuku with amusement and Cat’s cheeks burned, nodding wordlessly before going to pick up the discarded backpack, shouldering it on.

“Bye…Dad.”

She watched his amber gaze widen in surprise as she moved past him before he could beat her to it and she forced her sights on the door at the end of the hallway.

She had to get home. There was a battle going on.

Cat screamed as the sadistic monster that had greeted her in this place stood there, regarding her with sharp, glittering intelligent eyes.

“Temmie is very impressed. You spared him… that fool king.” The soft high-pitched sugary sweet voice warbled with laughter, sharp teeth glinting in the dim light. “But don’t think for an second… that you can change what happens. Temmie will be watching. You can pass, idiot creature.”

In a blink, the figure was gone and Cat was left shaking, hand frozen half-way to her tiara.

Fuck.

That.

The Senshi quickly rubbed her goose-pimpled arms and hesitantly trudged onward. Her sisters’ faces floated into her mind… Samantha’s soft smile and twinkling blue eyes, fierce violet eyes and a soothing lilting melody for Reiko, Kawa’s infuriating smirk and her billowing hair, and Alexis…

Alexis…

She had to get home.

Cat threw herself at the door, a desperate war cry tearing from her throat. The door refused to budge and **_ow._** Her skin burned and stung. She glanced at blood smeared onto the wood.

_Well. Huh._

She could always use her tiara…

Her hand found the ornament and watched as it glowed and spun until it was a spinning disk of her pink energy. It was soothing and she let it fly.

The disk crashed into the wood and clattered to the floor but it had forced the door open a crack… Cat sighed in resignation, adjusting her backpack and flinging her aching, tired body against the frame.

Home…Sam…Kawa…Reiko…

Alexis…

Usagi.

Cat fell face first into the snow and contemplated not getting up as the cold made her skin burn more and numbed the gashes. She reluctantly pushed herself up and opened her backpack, rummaging around.

She had the faded gold ribbon…the small plastic knife… the stick she had picked up to discourage the small monsters in the ruins from ambushing her… the thermos of golden flower tea that had been too hot to drink from Asgore… and the small jug of spicy whiskey from the weird dancing flames in the Ruins.

She had eaten the candy from the dish and the unusually spicy (but sweet) doughnut when she had been fighting and the bandage had fallen from her skin while she dodged. Cat sighed and grumbled at the lack of items that she knew would help her wounds heal and raise her energy levels. The stick would help at least.

She was so tired.

Taking a deep breath, Cat forced her weight to her feet and leaned heavily on the (thankfully) thick and sturdy stick and stumbled a few steps before she could walk in a semblance of a normal gait, muscles trembling and knees buckling under the purple cloak Asgore has given her.

_Shuffle. Crunch. Shuffle, shuffle, crunch, crunch…_

The snow beneath her boots made gentle noises, letting her mind empty and a semblance of relaxation return to her. Cat hummed to herself, the soft thudding of the stick keeping count of beats for her. It was almost peaceful.

Then the random branch laying in the middle of the path blocking her way had her growling fiercely.

_God damn it!_

Cat was tempted to kick it in her anger but it would be pointless. Frustratedly, she lifted a foot and gingerly increased her weight. She had to make sure it wouldn't break- no need for unnecessary injuries when she already was weak as it is. When it didn’t buckle, the rush of happiness gave her a much needed boost of energy and she lightly jumped into the snow.

Alright.

_Shuffle, thud, shuffle, crunch, crunch…_

**_Crack._ **

**_What the fuck?_ **

Cat turned around sharply and the branch lay broken behind her. Before she could think, her legs were pumping, stick clattering noisily along the ground, and her hair flying behind her.

**_Nope. No. Absolutely not._ **

There was a bridge up ahead and she powered toward it. She could make it.

Her lungs were burning and her wounds protested movement but she was so close.

Just a bit…

It felt like she slammed into a brick wall and she wheezed as her lungs constricted, a surprised yelp expelling what little air she had. Cat closed her eyes and waited for the painful tug on her soul or an attack.

She was so tired…

Instead she heard, “Don’t you know how to greet a new friend, human?”

_Friend?_

Cat found herself turning, orange wisps surrounding her body and a tall skeleton loomed over her, left eye burning with orange flames and hand outstretched. Smoke curled lazily around his skull from the cigarette floating by his teeth.

Cat gripped the stick in her hand, ready to defend but sudden her world toppled and darkened.


	2. -Out of Control-

**Summary for the Chapter:**

> Her magic is behaving weirdly and she needed someone to help. Even if that someone is a scary tall skeleton.

**Notes for the Chapter:**

> I forgot to mention this at the beginning: Sailor Cloud, Water, Star Mars, and Darkness all belong to their respective owners. I only own Sailor Cat. <3 Underswap also belongs to the AU creator.

Cat groaned at the pounding in her skull and the dull throb in her legs. She kept her eyelids closed, not wanting to fully awaken and curled her body. Something warm, soft, and sweet-smelling covered her and she pulled the blanket closer, sighing contentedly.

Just five more minutes and she would get up for class…

“Five minutes…” she mumbled out loud as a reassurance to the room, certain her sisters were nearby. “…I promise…”

Cat turned to get more comfortable on her side as her mind struggled from the last vestiges of sleep. She remembered feeling trapped, panic clawing at her chest and running, running, running… and a skeletal hand being offered before…

Cat jumped as memories broke through her grogginess and the blanket tightened as she flailed, arms and legs thrashing. She had been running from the skeleton! They had been following her! She fought against the squeezing fabric and tumbled from the mattress with a sharp cry of, “Fuck!” and groaned at the angry pins and needles from her body.

Wait.

She looked at herself and rubbed her temples at the sight. Her transformation had unraveled and she was in her school uniform, pink skirt covering just above her ankles and she tugged on the sleeves of her sailor shirt. Kristie sighed and scraped a palm across her face.

“That is…not good.” She murmured and let her fingers drift across her body, gingerly pressing on sore spots. “Let’s see how bad the burns are… travelling in the snow probably gave me frostbite- wha-what the…?”

Why had her wounds healed? Hiking her skirt up to inspect her thigh, Kristie blinked at the slightly reddened skin and stared at the lack of blood and blackened flesh.

“Well. Huh.”

At least _something_ was good but still…

Kristie rose to her feet and cupped her brooch.

“Cat Cosmic Power! Make UP!”

She felt the answering magic greet her and it travelled across her skin pleasantly, the mixing colors forming air-light ribbons and wrapping around her form. She didn’t notice the door being pushed open or the quiet footfalls of slippered feet as she got lost in her transformation and the comforting power sizzling across her skin.

“Hnng!”

The sharp pain in her chest made her drop to her knees and she watched in horror as the ribbon receded and left her, vulnerable, naked and exposed before her school uniform materialized. _Oh no. No, no, no…_

“You can use magic, human?”

Kristie’s hands flew up of her own accord and she watched in horror as Alexis’ sigil flashed before her eyes before a dark wave of ebony magic tore through her palms. She watched the tall skeleton take a step back before a single eye flashed orange.

_I’m not transformed! Why? Why? WHY?_

_STOP._

“STOP!” Kristie cried out, slamming her palms down and the magic followed her movements, crashing into the floor and writhing like an angry serpent. “Release!” She pictured Alexis’ symbol and watched it resist- struggling and burning her vision before it burst into black bubbles and the magic scattered across the carpet.

A surge of her own pink-tinted magic made a protective cyclone around her as she tried to breathe, clutching her skirt and vision blurred. The tears stung her eyes and she couldn’t stop shaking. Why was her powers activated when she wasn’t a Senshi?

“Human…” The voice was tight and guarded but Kristie focused on it. “If you don’t calm down, I will have to attack you.”

She couldn’t help it- she laughed, tears falling from her eyes. She was _tired, **tired, tired.**_ Kristie brushed her bangs from her eyes, smeared the tears away, and took in the skeleton- rigid posture, hands shoved into the orange hoodie, and clenched teeth.

“I…I don’t know why I’m here.” The words tumbled from her mouth and she lifted a shoulder in a half-hearted shrug. “I don’t know why my Senshi powers are activated. I don’t want to hurt you. I don’t want to FIGHT but I don’t know what is happening.”

The wisps of magic still circling her got tighter, closing in on her form before she threw one arm out and the cyclone died away. She could always control her own magic without problems... usually. “You said you were a friend, right?” Kristie’s words were soft and her mind screamed out that leaving herself vulnerable was insanity but what choice did she have?

She didn’t want to kill innocents. She was a _Senshi._

“My name is…Kristie. Who are you?”


End file.
